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Questions tagged [radio-frequency]

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Radio Waves / Light: Atmospheric Refraction

The following image differentiates between a visual horizon and a radar horizon. Sidenote: I'm not too familiar with primary surveillance radar technology, but this image refers to secondary ...
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1answer
52 views

Why aren't extremely-low-frequency (ELF) radio waves used for underwater radar?

Since extremely-low-frequency radio waves are used by submarines for some simple, low-transmission-rate communications, why can't those same wavelengths be used for submarine radar? It may not be ...
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1answer
38 views

Strange strong interference/noise in radio waves [closed]

Good night, Since 2014 when I bought my car I use a FM transmitter inside it to play my bluetooth musics, to escape for every radio in city I put the radio to work in the highest frequency it works ...
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0answers
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Would a radio frequency (RF) laser have any advantage over ordinary radios?

In the radio part of the electromagnetic spectrum it is really easy to make very clean and powerful RF waves using modern electronics, and it really isn't that hard to make arbitrary RF waves. But ...
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1answer
74 views

How does Event Horizon Telescope filter to get only the radio waves emitted by the target black hole?

There are many stars and black holes in the universe. So, their emitting radio waves may be mixed in the universe. How did the event horizon telescope filters to get only the radio waves emitted by ...
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12 views

The effect of dielectric bridges on the impedance of a coplanar waveguide

I'll start with some context, but feel free to skip to the third paragraph for the concrete question. I also posted it on the electronics stackexchange, but I think it might have some more chance here ...
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0answers
28 views

Power from human vs solar radio waves

I'm looking for a nicely presented comparison of solar radio waves and human-generated radio waves. The parameter I am most interested in is power. I imagine that human-generated radio waves exceed ...
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3answers
1k views

Could you use a laser beam as a modulated carrier wave for radio signal?

There have been successful experiments in modulating sound over a carrier ultrasound wave. Not so long ago, I've even seen an DIY implementation on Hackaday. I also encountered and tested a program ...
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3answers
195 views

Can radio waves be harmful to us?

I was studying about Microwaves and their action on water molecules in heating up the food. This all is probably due to Microwaves have wavelength such that it can be absorbed by water molecules (am i ...
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1answer
33 views

About sound of non-existent channels on FM

Well, I have learnt about resonant frequency due to series capacitor and inductor, and how the current at resonant frequency is highest, but i am confused about the sound, which appears even when no ...
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0answers
12 views

Determine Field of View from Given Simulation Box Size

I want to determine the field of view as would be seen by a telescope corresponding to a simulation box size(comoving) of, say 100^3 Mpc^3.As I understand the box size for simulation is a rough ...
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1answer
32 views

Identify the frequency antenna I can't access

I recently bought a (used) radio controlled airframe and buried deep inside the tail section is an antenna, broken out to some coax, with an SMA connector within the core of the fuselage. There is no ...
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1answer
52 views

How do LF Radio waves send data?

Excuse me I am a complete beginner. If LF radio waves are sent with let’s say frequencies of 100 kHz, how can data be modulated to that signal considering the signal is so long? For example, how can ...
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1answer
58 views

Why does S11 seem to be independent of transmission media in this RF transmission experiment?

Hi friends I am starting to characterize a system in which we will plan to measure the response of a sample of liquid to radio waves. In order to do this I am exciting two antennas with the ports of ...
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1answer
45 views

How RF receivers receive waves with bigger wavelenght than the distance between them?

I have a 27MHz RF toy car and I was wondering since the wavelenght is about 11 meters, when the car is closer to the remote than 11 meters how does the car receive the signal? Wouldn't the signal be ...
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0answers
11 views

Can radio waves be detected using a coulomb torsion balance?

Radio waves are almost everywhere. shouldn't the coulomb torsion balance be sensitive to any passing through the device?
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3answers
52 views

Why do sensors that emit higher frequency signals give more accurate data?

I am doing a technical presentation about RADAR and LiDAR. I understand that LiDAR is several times more accurate and capable of producing really detailed 3-D maps of their surroundings, while RADARs ...
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1answer
43 views

Best cantenna reflector type

If the reflector (closed end) of cantenna is shaped as parabolic dish, will it perform better than one with a flat reflector?
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1answer
26 views

Why is $Q$ factor an important quantity for electrical oscillations transmitting radio waves?

My textbook says that "$Q$ factor is an especially important quantity for electrical ossicilations trasnmitting radio waves. When selecting radio and television stations it is essential that the ...
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1answer
35 views

How can I calculate the total rotation a detuned pulse will apply a nuclear spin?

I'm trying to model the effect a radiofrequency pulse will have on a nuclear spin at different detunings. The pulse has a sech lineshape, a pulse area (time integral of the pulse envelope) of $\frac{π}...
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3answers
133 views

Can a lens be used at radio frequency?

Lenses and Antennas are two means of manipulating EM waves. While antennas are predominantly used at RF / Microwave frequencies, Lenses are used for optical/IR regions of the spectrum. I understand ...
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0answers
30 views

Are there Lasers in wavelenght of UHF or radio frequency?

how exists lasers in many wavelength in electromagnetic spectrum, like UV, VIS and IR. I don't know nothing about others wavelength as X-ray or radio frequency.
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2answers
74 views

How can Line of Sight work?

How can a mobile phone work inside a closed room with no openings if Line of Sight requires no obstacles between the receiver and transmitters? I know you may think it's not a Physics question but ...
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2answers
280 views

Why radio waves from radio-stations don't interfere with each other?

I know that radiowaves from radiostations are modulated either F.M or A.M . Lets suppose they are F.M and one has carrier wave frequency of 100 Hz and other 200 Hz they have F deviation of 20Hz/V . ...
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1answer
64 views

Does attenuation to RF waves increases with frequency?

I heard somewhere that RF waves at high frequency such as above 2GHz face more attenuation while passing through air, buildings and due to humidity as compared to 800Mhz and 2) Waves at 30-40GHz ...
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2answers
90 views

How are RF Waves transmitted?

What is the mode of transmission for RF waves at 1800 MHz. Is it ground wave propagation, Line of Sight Propagation or Atmospheric reflection (from ionosphere). What are the different ways for ...
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1answer
52 views

Why is power density of RF waves measured in m2?

Why is power density of RF waves measured in m2 or cm (Area) and not in cm3 or m3 (volume) ? I mean aren't those waves travelling (radiating) in 3D space? I am new to this topic so please pardon ...
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2answers
316 views

Electromagnetic Waves and GPS

If the global positioning system functions through radio waves, but radio waves are reflected in the ionosphere, then how do these electromagnetic waves reach the satellites?
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4answers
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What's the physics behind XKCD #2027 (time between lightning flash and radio wave burst)?

XKCD usually has solid (and often contemporary) science behind it. Lightning Difference, #2027 one says: Q: What’s that trick for telling how many miles away lightning is? A: Just count the ...
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1answer
260 views

Radio waves collision versus waves in a pond collision

Please see the attached picture: We are trying to show an image to visualize radio wave collision and interference with regards to Maritime AIS Technology. What do colliding radio waves have in ...
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6answers
6k views

Why put a radio telescope in space instead on the Moon?

Why are we not building a space-based radio telescope? If a lunar radio telescope is hard to build, why not a space-based radio telescope? It could be an interesting tool, I presume. Thus, what could ...
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2answers
5k views

What is the scientific explanation for radio waves bending around the Earth?

The experiment This experiment is documented in a documentary called Convex Earth. The exact location the following information is taken from starts at 14:25. High frequency directional antennas are ...
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1answer
216 views

Why radio waves can pass through walls but not infrared waves?

My physics teacher told that infrared waves are not passing through walls due to rayleigh scattering,but rayleigh scattering increases with increase in wavelength,then why radio waves are passing ...
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1answer
37 views

How do electrons in a conductor physically respond to radio waves?

If a radio wave hits a thick piece of metal, it's my understanding that the metal will for the most part reflect the wave. What I'm unclear about is how the electrons flow in a metal that's being ...
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1answer
292 views

Is Nylon RF transparent?

I was doing a research on which type clothes blocks the Radio frequency. Please also list the experiments which can be performed to determine such clothes/ materials.
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A shaped pulse as a sum of rectangular pulses

I have a pulse with lineshape $L(ω)=\frac{1}{π}\frac{\frac{1}{2}Γ}{((ω−ω_0)^2+(\frac{1}{2}Γ)^2)}$ in the frequency domain where $\Gamma$ is the pulse width and $\omega_0$ is the resonant frequency ...
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1answer
38 views

Why do satellite dish come in many different sizes?

Is it to do with how many photons can be absorbed in a given area? more surfaces mean more photons are absorbed but does it translate to better quality? btw can a single atom be as good as the largest ...
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4answers
132 views

Can the equation $E = h\nu$ be used not only for light, but for radio waves? (Since they are all part of the electromagnetic spectrum)

Can the equation $E = h\nu$ (or $E = hf$) be used to find the energy of the particles from the electromagnetic spectrum? I mean, for example light is part of the EM, a radio wave is also part of the ...
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0answers
20 views

Effect of a Lorentzian pulse on a non-resonant spin particle

I'm looking into rotation of a nuclear spin particle using a pulse with a Lorentzian lineshape. If the pulse has an area of $\frac{\pi}{2}$ and the nuclear spin frequency is on resonance with the ...
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1answer
40 views

Modelling a radiofrequency pulse

I'm looking into NMR at the moment and am trying to work out a way of modelling the action of a radiofrequency pulse on nuclear spins. Specifically, if I apply a pulse to rotate the spin by $\pi/2$ I ...
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0answers
236 views

advantages or disadvantages of pulsed laser vs continuous-wave (CW) laser

What are the advantages and disadvantages of pulsed vs CW laser? Does pulsed laser have more power compared to CW laser, or it is vice versa? If I have to guess, for long distance communication, ...
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2answers
119 views

Communications: Ground wave Propagation

(I wasn't having any tag for this question(Example: Communication-Systems, Modern-physics.)) I was studying ground wave propagation, my book writes the lines about it without explaining it. I really ...
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3answers
112 views

L-band for search radars?

I'm making my way through the Linesman-related section's of Gough's Watching the Skies. Linesman was developed to counter the carcinotron jammer. The main solution was the Type 85, which had 12 ...
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2answers
1k views

Why doesn't the ${\rm H}_2$ molecule have a permanent dipole while the neutral ${\rm H}\,{\rm\small I}$ has one?

According to the National Radio Astronomy Observatory, the $21\,{\rm cm}$ line of hydrogen can be emitted by the neutral hydrogen atom due to the magnetic interaction between the spins of the proton ...
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2answers
458 views

Reflection of radio waves at an obstacle with size half wavelength

I'm following a course about communication technology and the professor said the following multiple times: "A radio/EW-wave is reflected at an obstacle which is higher/larger than than half of the ...
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2answers
156 views

(Please Explain) Clarification on extraterrestrial communication with radio waves

I just want to get some clarifications regarding the transmission and receiving of a radio waves between planets as a means of communication with aliens for story building. Is it better to transmit ...
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2answers
132 views

Why don't radio waves ruin electronics?

Out of curiosity, I estimated the voltage amplitude for typical visible light. Wikipedia says that sunlight hits the earth at about $1000 W / m^2$. The intensity of an electric field is given by $$I =...
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1answer
308 views

Does a Faraday Cage need to be sealed to block RF?

I was watching a program on shoplifting and there were things called booster bags shown, which blocked a security tag which acts as an LC resonator when put between the security towers, causes the ...
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1answer
429 views

Power losses for electromagnetic waves radiation in copper wire with high frequency current [closed]

How to calculate electric power losses to radiation of electromagnetic waves in copper wire with high-frequency current? For example, I have a copper wire with known diameter and length and I send ...
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0answers
52 views

Magnet on a piezo - Can this oscillating field give me a radio transmitter?

I can read on wikipedia that radio waves are of frequency 3kHz-3THz. I know that piezoelectric actuator can reach eg. 20 kHz. What would happen if I put a small neodymium magnet on a piezoelectric ...